[foxforever90]

Hi All,
Been lurking for a long time... Forgive me up, if I violate forum etiquette. It's been a really long time since I've posted in any forum.

Ok, I have an Avid CNC(cncrouterparts at the time) 24 x 48 cnc router. I have a Dell optiplex 7xx running linuxCNC and a g540 driving everything. The setup was very budget friendly at the time and it has worked very well for a long time (10+ yrs). However, I've started to notice issues. One came to light very recently while attempting to machine guns grips for a friend.

While running a 3D contour toolpath to create the overall surface profile (requiring lots of z motion) I noticed the z axis drift upward and it became very noticeable at the end of the program, i.e. ~0.040" higher than z zero (on a part only 0.15" thick).

So I tried to troubleshoot the best I could. Checked all the mechanicals on z. Reduced velocity and acceleration many times. Tried running the toolpath in open air. Separated control cables from router and vacuum (thought it might be a noise issue). Nothing changed. Same result every time. So then I decide to crack open the g540. Looked over all the drives. I noticed what appeared to be a couple cold solder joints but really didn't know what to make of it. So I just decided to swap z with y. Put it all back together ran the program. The surface was looking better than ever but then... yup now the y axis did the same thing. Drifts in negative direction.

My question... Is this a good indicator of a bad drive? Would it make sense just to purchase a spare g250x or should I send the whole thing (g540) back to gecko to go thru it? Reason I say that is I've noticed a lot of glitchy motion, motors seem to hiccup as I move the machine throughout its range of travel.

[awerby]

It sounds like the Z axis was losing steps on the plunge, which makes it think it's gotten lower than it really has, so it raises up higher on the return stroke. If the error follows along when you switch leads to another axis, that indicates a problem upstream, probably with the drive. But fortunately, the G540 has 4 drives, and if you aren't running a 4th axis, that means there's a spare one you can remap to Z. I'd suggest trying that, and sending the suspect drive back to Geckodrives to see if it can be repaired, or needs to be replaced. (You should be able to remove it and keep using the other three.) Geckodrives is generally pretty good about supporting their equipment. But if it's been working for over 10 years, it might just have succumbed to old age.

[foxforever90]

Yeah, seems like the problem followed the driver. I didn't swap any cables, just the drives within the g540 (moved z to y). Unfortunately, my setup uses 2 drives for the gantry (x axis) so I don't have a spare. Was thinking of just buying a spare g250x but thought there may be some benefit to sending the entire g540 back to gecko.

[foxforever90]

Anyone have an idea on the cost for gecko to do 'typical' repairs? I.e. troubleshoot and replace or repair a drive?